Polyamide composition containing a metallic pigment

ABSTRACT

The polymer composition containing a polyamide resin, a metallic pigment, and a carrier is disclosed that exhibits a metallic appearance.

RELATED APPLICATIONS

The present application is based upon and claims priority to U.S.Provisional Patent Application No. 62/281,676, filed on Jan. 21, 2016,which is incorporated herein by reference.

BACKGROUND

Thermoplastic polymers are a class of polymers that soften above aspecific temperature and therefore are moldable into all different typesof shapes and forms. The polymers solidify upon cooling. Many differenttypes of thermoplastic polymers exist. The polymers can have differentproperties depending upon their molecular structure.

Thermoplastic polymers are used in numerous and diverse applications.The polymers are generally lighter and less expensive than metals. Infact, those skilled in the art continue to strive to replace partsconventionally made from metal and wood with those made fromthermoplastic polymers. In many instances, the polymers offer variousadvantages with respect to chemical resistance, fatigue resistance,flexural modulus, and/or cost.

One problem that has been encountered in producing molded polymerarticles, however, is the ability to produce articles with a distinctivelook or appearance. Many thermoplastic polymers, for instance, have adull appearance when combined with various pigments and dyes. Problemshave been experienced in the past in incorporating pigments and dyesinto the polymers so that the pigments and dyes uniformly disperse in amanner that allows for the molding of products and parts that have anoverall aesthetic appearance.

Various problems, for instance, have been experienced in the past inattempting to incorporate pigments and dyes into polyamide polymers,which are also known as nylon polymers. For instance, the variety ofproblems that have been experienced include poor incorporation ordistribution of the pigment or dye within the polymer, low loadinglevels that fail to produce a meaningful color effect with uniformproperties, and the formation of flow lines, gate blush, or otherimperfections in the surface of the polymer when molded.

In view of the above, a need exists for a formulation and process forincorporating pigments and dyes into thermoplastic polymers, such aspolyamide polymers. For example, in one embodiment, a need exists forincorporating metallic pigments into polyamide polymers for producingproducts, parts and articles that have an overall metallic appearance.

SUMMARY

In general, the present disclosure is directed to polymer compositionscontaining a metallic pigment. The metallic pigment is incorporated intothe polymer composition in a manner such that molded products made fromthe composition can have a metallic appearance. Products made accordingto the present disclosure can be used in numerous applications. Forinstance, products made according to the present disclosure may be usedas automotive parts (such as automotive interior parts), consumerappliance parts, and the like.

In one embodiment, for instance, the present disclosure is directed to apolymer composition comprising a polyamide resin. The polyamide resin,for example, may be present in the polymer composition in an amountgreater than about 60% by weight, such as in an amount greater thanabout 70% by weight, such as in an amount greater than about 80% byweight, such as in an amount greater than about 90% by weight. Ingeneral, the polyamide polymer is present in an amount less than about99.9% by weight, such as in an amount less than about 99.5% by weight.

In accordance with the present disclosure, the polyamide resin iscombined with a metallic pigment, such as an aluminum pigment, and acarrier for the metallic pigment. In one embodiment, the carrier isadded in relatively great amounts in relation to the pigment in order todisperse the pigment within the polymer matrix. For instance, the weightratio between the carrier and the metallic pigment can be from about 1:9to about 2:1, such as from about 3:17 to about 1:1. In one embodiment,for instance, the weight ratio is from about 1:4 to about 2:3.

The metallic pigment may have any suitable shape. For instance, thepigment may comprise spherical particles. In one embodiment, however,the metallic pigment has a plate-like shape. For instance, the pigmentcan have an aspect ratio of greater than about 4:1, such as greater thanabout 8:1. For example, the metallic pigment can have an average medianparticle size (D50) of from about 2 microns to about 80 microns, such asfrom about 12 microns to about 60 microns. Particle size can be measuredusing microscopic examination and/or laser diffraction. The metallicpigment can be present in the polymer composition in an amount fromabout 0.5% to about 10% by weight, such as in an amount from about 2% toabout 8% by weight. The metallic particles may be polished and have alenticular appearance.

Especially when incorporating a metallic pigment having plate-likeparticles into the composition, the carrier can comprise a polymer, anoil, or a wax. For instance, the carrier may comprise a polyolefinpolymer, such as a polyethylene polymer. Alternatively, the carrier maycomprise a hydrocarbon oil, such as a mineral oil. In still anotherembodiment, the carrier may comprise a wax, such as a montan wax.

Molded articles made according to the present disclosure, in oneembodiment, can be produced so as to have a high gloss surfaceappearance. For instance, articles made according to the presentdisclosure can have an exterior surface that exhibits a gloss of greaterthan 40 gloss units when measured at a 60° angle using a glossmeter. Forexample, the exterior surface of the article may exhibit a gloss ofgreater than about 50 gloss units, such as greater than about 80 glossunits when measured at a 60° angle.

The polymer composition may further contain various other componentsdepending upon the particular application. In one embodiment, forinstance, the polymer composition can contain a lubricant. The lubricantmay comprise, for instance, a metal salt of a fatty acid such as zincstearate.

Other components that may be added to the polymer composition include UVstabilizers, antioxidants, and/or a hindered amine light stabilizer. Theabove components may be present in the polymer composition in an amountgenerally less than about 2% by weight, such as in an amount less thanabout 1% by weight. Each of the above components, for instance, may bepresent in the composition in an amount greater than about 0.01% byweight, such as in an amount greater than about 0.05% by weight, such asin an amount greater than about 0.1% by weight.

Other features and aspects of the present disclosure are discussed ingreater detail below.

DETAILED DESCRIPTION

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the presentdisclosure.

In general, the present disclosure is directed to molded polymeric partshaving a metallic finish. The present disclosure is also directed to apolymer composition for producing the parts and to a molding processusing the composition. In general, the polymeric parts are formed from acomposition containing a thermoplastic polymer, such as a polyamidepolymer, a metallic pigment, and/or various other components, such as acarrier and/or a lubricant.

In one embodiment, the metallic pigment is incorporated into the polymercomposition in conjunction with a carrier for the pigment. For example,the carrier can improve not only handling of the pigment and dispersionof the pigment into the composition, but has also been found to improvemelt processing of the polymer composition. In particular, it wasunexpectedly discovered that using a carrier in certain amounts actuallyimproves the ability of the composition to be extruded. The carrier, forinstance, may comprise a polymer, a wax, or an oil. In general, themetallic pigment and carrier are combined together so that the carrieris present in an amount of at least 10% by weight, such as in an amountof at least 15% by weight, such as in an amount of at least 20% byweight, such as in an amount of at least 25% by weight, such as in anamount of at least 30% by weight, based upon the total weight of themetallic pigment and carrier together. In general, the carrier ispresent with the pigment in an amount less than about 60% by weight,such as in an amount less than about 50% by weight, based upon the totalweight of the metallic pigment and carrier.

The polymer composition of the present disclosure contains at least onethermoplastic polymer. In one embodiment, the thermoplastic polymercomprises a polyamide polymer either alone or in combination with otherthermoplastic polymers. Other thermoplastic polymers that may be presentinclude polyolefins, polyesters, polycarbonates, and the like.

In general, any suitable polyamide polymer may be used in accordancewith the present disclosure. Illustrative examples of suitablepolyamides include those derived from lactams with 7- to 13-memberedrings, such as polycaprolactam, polycaprylyl lactam, and polylauryllactam, as well as polyamides obtained by a reaction of a polycarboxylicacid, preferably a dicarboxylic acid, with a polyamine, preferably adiamine. Examples of suitable polyacids include, without limitation,alkanedicarboxylic acids having at least about 6 carbon atoms and up toabout 12, preferably up to about 10, carbon atoms; and aromaticdicarboxylic acids. Particular examples include adipic, azelaic,sebacic, dodecanedicarboxylic, terephthalic, phthalic, and isophthalicacids and anhydrides and mixtures of these. Suitable polyamines include,without limitation, alkanediamines having at least about 6 carbon atomsand alkanediamines having up to about 12, preferably up to about 8,carbon atoms. Particular examples of useful polyamines arem-xylylenediamine, di-(4-aminophenyl)methane,di-(4-aminocyclohexyl)methane, 2,2-di-(4-aminophenyl)propane,2,2-di-(4-aminocyclohexyl)propane, and mixtures of these.

Examples of nylons (polyamides) that may be used in the processes andcompounds of the disclosure include, without limitation, nylon-6,nylon-6,6, nylon-6,10, nylon-4,6, nylon-6,12, nylon-11, nylon-12, nylon6/66, partially aromatic nylon copolymers such as nylon-6/6, T,nylon-6,6/6, I/6, T; and so on, and mixtures and blends of these.

In one embodiment, the composition includes nylon-6, which may beproduced by the polymerization of caprolactam.

The polyamides that may be used in the present disclosure can havenumber average molecular weights of at least about 10,000, such as atleast about 15,000. The number average molecular weights of thepolyamide may be up to about 200,000, such as up to about 100,000, suchas up to about 50,000, such as up to about 30,000. It should beunderstood, however, that any suitable polyamide resin may be used thatcan have a number average molecular weight outside of the above ranges.The polyamide resins used to prepare the compositions can have apolydispersity of less than about 4, such as less than about 2.5 in oneembodiment.

The polyamide polymer is generally present in the polymer composition inan amount greater than about 60% by weight, such as in an amount greaterthan about 70% by weight, such as in an amount greater than about 80% byweight, such as in an amount greater than about 85% by weight, such asin an amount greater than about 90% by weight, such as in an amountgreater than about 91% by weight. The polyamide polymer is generallypresent in the composition in an amount less than about 99.9% by weight,such as in an amount less than about 99.5% by weight.

The composition may further optionally include a lubricant. Examples ofsuch lubricants include fatty acids esters, the salts thereof, esters,fatty acid amides, organic phosphate esters, and hydrocarbon waxesincluding mixtures thereof. Suitable fatty acids typically have abackbone carbon chain of from about 12 to about 60 carbon atoms, such asmyristic acid, palmitic acid, stearic acid, arachic acid, montanic acid,octadecinic acid, parinric acid, and so forth. Suitable esters includefatty acid esters, fatty alcohol esters, wax esters, glycerol esters,glycol esters and complex esters. Fatty acid amides include fattyprimary amides, fatty secondary amides, methylene and ethylene bisamidesand alkanolamides such as, for example, palmitic acid amide, stearicacid amide, oleic acid amide, N,N′-ethylenebisstearamide and so forth.Also suitable are the metal salts of fatty acids such as calciumstearate, zinc stearate, magnesium stearate, and so forth; hydrocarbonwaxes, including paraffin waxes, polyolefin and oxidized polyolefinwaxes, and microcrystalline waxes.

When employed, the lubricant(s) typically constitute from about 0.001%by weight to about 2% by weight, and in some embodiments, from about0.005% by weight to about 0.1% by weight of the thermoplasticcomposition. In one embodiment, the lubricant may comprise a metalstearate, such as zinc stearate. The zinc stearate may be present in anamount from about 0.01% to about 0.05% by weight. It was found that evensmall amounts of a metal stearate can significantly improve theprocessing properties of the composition. Further, in the past,polyamide polymers were typically combined with copper compounds, suchas copper iodide, as a lubricant. Copper compounds, however, canadversely interfere with the metallic pigment and/or the polyamidepolymer during processing and can ultimately discolor the resultingproducts. Thus, in one embodiment, the polymer composition of thepresent disclosure contains no copper compounds, such as copper iodide.

In accordance with the present disclosure, the thermoplastic polymer,such as the polyamide polymer, is combined with a metallic pigment. Ingeneral, any suitable metallic pigment may be used in accordance withthe present disclosure. For instance, the metallic pigment may have anysuitable shape. The metallic pigment particles may be spherical and canhave an aspect ratio of less than about 4:1, such as from about 1:1 toabout 4:1.

In one particular embodiment of the present disclosure, however,metallic pigment particles are used that have a plate-like shape.Plate-shaped particles have been found to provide various advantages andbenefits. The plate-like particles, for instance, can produce articleshaving a more metallic appearance, especially if the plate-likeparticles are uniformly dispersed within the polymer matrix.

In one embodiment, the particles can be polished or otherwise have ahigh reflectivity and can be lenticular or have a flake shape (silverdollar or cornflake shape). In one embodiment, the plate-like particlescan have an aspect ratio of greater than about 4:1, such as greater thanabout 8:1, such as from about 10:1 to about 300:1. The plate-likeparticles can have a median diameter of generally greater than about 12microns, such as greater than about 14 microns. The plate-like particlescan have a median diameter of generally less than about 100 microns,such as less than about 70 microns, such as less than about 60 microns.In one embodiment, the particle size of the metallic pigments rangesfrom about 15 microns to about 55 microns.

In one embodiment, the metallic pigment may comprise an aluminum pigmentthat contains elemental aluminum. The aluminum pigment, for instance,can be very thin having a thickness of less than about 1 micron and canhave a median diameter as described above. The aluminum pigment can havea pronounced flop, a high brilliance and be highly reflective.

In one embodiment, the aluminum pigment can contain greater than about80% by weight aluminum. The aluminum pigment can be present alone or incombination with other additives, such as a carrier. In fact, in oneembodiment, the metallic pigment is combined with a carrier and theresulting blend is incorporated into the polymer composition. Thecarrier can not only facilitate dispersing the metallic pigment into thepolymer matrix, but can also improve the melt processing characteristicsof the polymer composition.

In one embodiment, for instance, the metallic pigment is combined with acarrier prior to being combined with the thermoplastic polymer, such asthe polyamide polymer. The carrier can be present in relatively greatamounts in relation to metallic pigment. For instance, the weight ratiobetween the carrier and the metallic pigment can be greater than about1:9, such as greater than about 3:17, such as greater than about 1:4.The weight ratio is generally less than about 2:1, such as less thanabout 1:1, such as less than about 2:3. In one particular embodiment,the weight ratio between the carrier and the metallic pigment is fromabout 1:4 to about 3:10. The carrier in the above amounts isparticularly well suited for incorporating a metallic pigment that has aplate-like shape into the polymer composition.

Various different carriers may be used in conjunction with the metallicpigment. In one embodiment, for instance, the carrier may comprise apolymer, such as a polyolefin polymer. The polyolefin polymer, forinstance, can have a relatively low molecular weight and may comprise apolypropylene polymer, a polyethylene polymer, or the like. Thepolyolefin polymer may comprise a homopolymer or a copolymer. In oneembodiment, the carrier comprises a polyethylene wax.

In an alternative embodiment, the carrier may comprise any suitable wax,such as a montan wax. In yet another embodiment, the carrier maycomprise a hydrocarbon oil, such as a mineral oil. For instance, thehydrocarbon oil may be comprised primarily of alkanes having a carbonchain length greater than about 9 carbon atoms.

The amount of metallic pigment incorporated into the polymer compositioncan vary depending upon the particular application. In general, themetallic pigment is present in an amount greater than about 0.5% byweight, such as in an amount greater than about 1% by weight, such as inan amount greater than about 2% by weight. The metallic pigment isgenerally present in an amount less than about 12% by weight, such as inan amount less than about 10% by weight, such as in an amount less thanabout 8% by weight. In one particular embodiment, the metallic pigmentis present in an amount from about 2% to about 8% by weight, such asfrom about 2% to about 6% by weight. For example, in one embodiment, themetallic pigment is present in the polymer composition in an amount fromabout 2% to about 4% by weight. When higher gloss characteristics areneeded, however, the metallic pigment may be present in an amount fromabout 4% to about 6% by weight.

Of particular advantage, the present inventors discovered that firstproducing a masterbatch containing the metallic pigment and polyamidepolymer is generally not necessary when incorporating the metallicpigment into the polyamide polymer. For instance, it is generally notnecessary to first produce a polyamide composition containing a highlyconcentrated metallic pigment which is then later combined with furtheramounts of a polyamide polymer.

In addition to a polyamide polymer resin, a metallic pigment, a carrier,and optionally a lubricant, the polymer composition can also containvarious other additives and components. The various other additives andcomponents may be present in the composition in an amount up to about 5%by weight, such as in an amount from about 0.001% to about 2% by weight.In one embodiment, for instance, each additional additive or componentis present in an amount less than about 1% by weight.

In one embodiment, for instance, the polymer composition mayadditionally contain an ultraviolet light stabilizer. As used herein, anultraviolet light stabilizer comprises a material that absorbsultraviolet light. In particular, the ultraviolet light stabilizerabsorbs ultraviolet light in order to prevent the ultraviolet light fromdiscoloring or otherwise adversely interfering with the polymer.

In one embodiment, the ultraviolet light stabilizer comprises abenzophenone, a benzotriazole, or a benzoate. Particular examples ofultraviolet light stabilizers include 2,4-dihydroxy benzophenone,2-hydroxy-4-methoxybenzophenone,2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole,2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole,2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,2-hydroxy-4-octoxybenzophenone, and 5,5′-methylenebis(2-hydroxy-4-methoxybenzophenone);2-(2′-hydroxyphenyl)benzotriazoles, e.g.2-(2′-hydroxy-5′-methylphenyl)benzotriazole,2-(2′-hydroxy-5′-t-octylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole,2-(2′-hydroxy-3′,5′-di-t-butylphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole,2-(2′-hydroxy-3′,5′-dicumylphenyl)benzotriazole, and 2,2′-methylenebis(4-t-octyl-6-benzotriazolyl)phenol, phenylsalicylate, resorcinolmonobenzoate, 2,4-di-t-butylphenyl-3′,5′-di-t-butyl-4′-hydroxybenzoate,and hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate; substituted oxanilides,e.g. 2-ethyl-2′-ethoxyoxanilide and 2-ethoxy-4′-dodecyloxanilide;cyanoacrylates, e.g. ethyl-α-cyano-β,β-diphenylacrylate andmethyl-2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate, or mixturesthereof.

Still another additive that may be present in the composition is asterically hindered phenol compound, which may serve as an antioxidant.Examples of such compounds, which are available commercially, arepentaerythrityltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010,BASF), triethylene glycolbis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] (Irganox 245,BASF), 3,3′-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionohydrazide](Irganox MD 1024, BASF), hexamethylene glycolbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 259,BASF), and 3,5-di-tert-butyl-4-hydroxytoluene (Lowinox BHT, Chemtura).Preference is given to Irganox 1010 and especially Irganox 245. Theabove compounds may be present in the composition in an amount less thanabout 2% by weight, such as in an amount from about 0.01% to about 1% byweight.

Light stabilizers that may be present in addition to the ultravioletlight stabilizer in the composition include sterically hindered amines.Hindered amine light stabilizers that may be used include oligomericcompounds that are N-methylated. Examples of light stabilizers include2,2,6,6-tetramethyl-4-piperidyl compounds, e.g.,bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (Tinuvin 770, BASF) or thepolymer of dimethyl succinate,1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine (Tinuvin622, BASF),Bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate(Tinuvin PA 144), or3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane(Adeka Stab LA 63P). The light stabilizers, when present, can beincluded in amounts greater than about 0.1% by weight, such as inamounts greater than about 0.5% by weight, but in an amount less thanabout 2% by weight, such as in an amount less than about 1% by weight.

Fillers that may be included in the composition include glass beads,wollastonite, loam, mica, molybdenum disulfide or graphite, inorganic ororganic fibers such as glass fibers, carbon fibers or aramid fibers. Theglass fibers, for instance, may have a length of greater than about 3mm, such as from 5 to about 50 mm. Many of the above fillers can bepresent in the polymer composition in an amount less than about 2% byweight. In other embodiments, however, a filler may be present in anamount greater than 2% by weight, especially when the compositioncontains reinforcing fibers. For example, in one embodiment, fillers canbe present in the composition in an amount from about 2% to about 15% byweight, such as from about 5% to about 10% by weight.

In addition to the metallic pigment, the polymer composition may alsocontain a coloring agent. The coloring agent may comprise any suitablepigment or dye. The pigment may comprise an inorganic pigment or anorganic pigment. Pigments that may be present in the compositioninclude, for instance, titanium dioxide, ultramarine blue, cobalt blue,phthalocyanines, anthraquinones, mixtures thereof, and the like. Othercoloring agents can include carbon black or various otherpolymer-soluble dyes. The coloring agents can be present alone or incombination in an amount up to about 2% by weight, such as in an amountfrom about 0.01% to about 1% by weight.

The polymer composition of the present disclosure can be used to producevarious molded parts. The parts can be formed through any suitablemolding process, such as an injection molding process or through a blowmolding process. Polymer articles that may be made in accordance withthe present disclosure include knobs, door handles, automotive panels,interior automotive parts such as bezels, consumer appliance parts, andthe like without limitation.

As described above, the polymer composition of the present disclosureproduces molded parts having a metallic appearance. For example, partsmade according to the present disclosure can have high glosscharacteristics if desired. Gloss is the characteristic or attribute ofan exterior surface that causes the surface to have a shiny, lustrousand/or metallic appearance. Gloss is generally dependent upon the mannerin which light is reflected off of a surface. A high gloss surfacegenerally reflects incident light primarily at the same angle at whichthe light is incident upon the surface. Surfaces with less gloss, forinstance, have a tendency to scatter light in all directions as thelight reflects off the surface.

Gloss can be measured by reflecting light off of a surface at aparticular angle and then measuring reflection using a glossmeter. Moreparticularly, gloss is measured by shining a known amount of light at asurface and quantifying the reflectance. A glossmeter directs a light ata specific angle to a test surface and simultaneously measures theamount of reflection.

Surfaces made in accordance with the present disclosure exhibit highmetallic brilliance. In particular, the molded parts may exhibit a glossof greater than about 40 gloss units when measured at a 60° angle usinga glossmeter. More particularly, molded parts in accordance with thepresent disclosure may exhibit a gloss of greater than about 50 glossunits, such as greater than about 80 gloss units, such as greater thanabout 90 gloss units, when measured at a 60° angle. In general, thesurfaces exhibit a gloss of less than about 150 gloss units, such asless than about 136 gloss units, at a 60° angle. Gloss can be measuredat a 60° angle according to ASTM Test D-523-08.

In addition to having excellent gloss characteristics, molded articlesmade according to the present disclosure can also have excellent colorproperties. Color can be quantified by measuring the absorbence with anoptical reader in accordance with a standard test methodology known as“CIELAB”, which is described in Pocket Guide to Digital Printing by F.Cost, Delmar Publishers, Albany, N.Y. ISBN 0-8273-7592-1 at pages 144and 145 and “Photoelectric color difference meter”, Journal of OpticalSociety of America, volume 48, page numbers 985-995, S. Hunter, (1958),both of which are incorporated herein by reference in their entirety.More specifically, the CIELAB test method defines three “Hunter” scalevalues, L*, a*, and b*, which correspond to three characteristics of aperceived color based on the opponent theory of color perception and aredefined as follows:

L*=Lightness (or luminosity), ranging from 0 to 100, where 0=dark and100=light;

a*=Red/green axis, ranging from −100 to 100; positive values are reddishand negative values are greenish; and

b*=Yellow/blue axis, ranging from −100 to 100; positive values areyellowish and negative values are bluish.

In accordance with the present disclosure, for instance, molded articlescontaining a metallic pigment can have an L* value that is greater thanthe L* value of the polyamide polymer not containing the metallicpigment.

In general, the L* value can be greater than about 70, such as greaterthan about 74, such as greater than about 76, such as greater than about78, such as greater than about 80, such as even greater than about 82.The L* color value is generally less than about 95, such as less thanabout 90.

The present disclosure may be better understood with reference to thefollowing example.

Example

Various polyamide polymer compositions were formulated containing analuminum pigment and a carrier. The resulting compositions were testedfor gloss and color values. The polyamide polymer used was apolycaprolactam polymer.

The polyamide polymer was combined with various different blends of analuminum pigment and a carrier. In particular, the following aluminumpigment and carrier blends were tested at different weight percentages.

Sample wt. % Al pigment No. and particle size wt. % carrier 1 80% 28micron 20% PE wax 2 70% 40 micron 30% PE wax 3 80% 15 micron 20% montanwax 4 70% 24 micron 30% PE wax 5 80% 55 micron 20% mineral oil 6 80% 34micron 20% PP wax

The following results were obtained:

L* a* b* Gloss @ 60° Polyamide 78.39 −1.88 −0.35 96.0 resin Sample No. 10.5% 68.19 −0.52 −0.44 96.5   1% 71.17 −0.57 −0.93 99.0   2% 73.50 −0.58−1.26 99.3   4% 74.63 −0.6 −1.50 99.9   8% 74.86 −0.6 −1.57 95.3 SampleNo. 2 0.5% 65.86 −0.79 −1.30 95.1   1% 66.50 −0.52 −0.22 95.5   2% 68.23−0.47 −0.05 95.3   4% 70.27 −0.44 −0.17 90.8   8% 72.21 −0.44 −0.47 90.2Sample No. 3 0.5% 74.82 −0.51 −0.29 105   1% 77.69 −0.55 −0.78 107   2%79.98 −0.56 −1.13 112   4% 81.91 −0.57 −1.30 110   8% 83.69 −0.55 −1.38105 Sample No. 4 0.5% 69.33 −0.39 −0.31 99.9   1% 72.17 −0.44 −0.06 100  2% 74.61 −0.45 −0.39 102   4% 77.83 −0.47 −0.67 100   8% 79.27 −0.46−0.86 93.7 Sample No. 5 0.5% 65.07 −0.34 −0.47 97.6   1% 65.35 −0.32−0.13 97.4   2% 66.99 −0.39 −0.45 96.0   4% 69.91 −0.43 −0.82 90.4   8%71.40 −0.45 −1.02 87.2 Sample No. 6 0.5% 68.24 −0.47 −0.51 98.8   1%79.87 −0.54 −0.34 98.4   2% 72.98 −0.54 −0.72 98.6   4% 75.44 −0.56−1.03 96.1   8% 76.29 −0.56 −1.24 91.8

These and other modifications and variations to the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention, which ismore particularly set forth in the appended claims. In addition, itshould be understood that aspects of the various embodiments may beinterchanged both in whole or in part. Furthermore, those of ordinaryskill in the art will appreciate that the foregoing description is byway of example only, and is not intended to limit the invention sofurther described in such appended claims.

What is claimed:
 1. The polymer composition for producing moldedproducts having a metallized appearance, the polymer composition beingformed by the following process: combining a polyamide polymer with acarrier and a metallic pigment blend, the carrier being present in theblend such that the weight ratio between the carrier and the metallicpigment is from about 1:9 to about 2:3, the carrier comprising apolyolefin homopolymer, a polyolefin copolymer, a montan wax, or ahydrocarbon oil, the metallic pigment being in the form of plate-likeparticles, the particles having a median particle size of from about 2microns to about 100 microns and an aspect ratio of greater than about4:1, the metallic pigment having a thickness of less than 1 micron, themetallic pigment being present in the composition in an amount of fromabout 0.5% to about 12% by weight; the polyamide polymer present in thecomposition in an amount of at least about 70% by weight; and whereinthe polymer composition is free of fillers and reinforcing fibers. 2.The polymer composition as defined in claim 1, wherein the carriercomprises a polyolefin polymer, and wherein the weight ratio between thecarrier and the metallic pigment is from about 3:17 to about 2:3.
 3. Thepolymer composition as defined in claim 1, wherein the carrier comprisesthe hydrocarbon oil.
 4. The polymer composition as defined in claim 1,wherein the carrier comprises a polyethylene wax.
 5. The polymercomposition as defined in claim 1, wherein the composition is free ofcopper compounds.
 6. The polymer composition as defined in claim 1,wherein the metallic pigment comprises an aluminum pigment.
 7. Thepolymer composition as defined in claim 1, further containing alubricant.
 8. The polymer composition as defined in claim 7, wherein thelubricant comprises a metal stearate.
 9. The polymer composition asdefined in claim 1, wherein the thermoplastic polymer resin comprisesnylon-6 or nylon-6,6.
 10. The polymer composition as defined in claim 1,wherein the polymer composition further contains an antioxidant, ahindered amine light stabilizer, and an ultraviolet light stabilizer.11. The polymer composition as defined in claim 1, wherein the metallicpigment particles have an aspect ratio of greater than about 8:1. 12.The polymer composition as defined in claim 1, wherein the metallicpigment is present in the polymer composition in an amount from about 2%to about 6% by weight.
 13. The polymer composition as defined in claim1, wherein the metallic pigment particles have a median particle size(D50) of from about 12 microns to about 60 microns.
 14. The polymercomposition as defined in claim 1, wherein the carrier comprises amineral oil.
 15. The polymer composition as defined in claim 1, whereinthe polymer composition, when tested for gloss, produces a gloss greaterthan about 90 gloss units when measured at a 60° angle according to ASTMTest D-523-08.
 16. The polymer composition as defined in claim 1,wherein the carrier is the montan wax.
 17. The polymer composition forproducing molded products having a metallized appearance, the polymercomposition being formed by the following process: combining a polyamidepolymer with a carrier and a metallic pigment blend, the carrier beingpresent in the blend such that the weight ratio between the carrier andthe metallic pigment is from about 1:9 to about 2:3, the carriercomprising a polyolefin homopolymer, a polyolefin copolymer, a montanwax, or a hydrocarbon oil, the metal pigment comprising an aluminumpigment, the metallic pigment having a thickness of less than 1 micron,the metallic pigment being present in the composition in an amount offrom about 0.5% to about 12% by weight; the polyamide polymer present inthe composition in an amount of at least about 70% by weight; andwherein the polymer composition is free of fillers and reinforcingfibers.